1. Field of the Invention
The invention relates in general to the method of inspecting a defect on a translucid film, and more particularly to the method of inspecting a defect on a translucid film by adding an anti-reflective coating (ARC) on the translucid film.
2. Description of the Related Art
In the semiconductor process, after forming an translucid layer, for example, an oxide layer, on a semiconductor substrate by deposition, there is usually a following polishing step to flatten the surface of the translucid layer. The preferred polishing is chemical mechanical polishing (CMP). After polishing, the engineers inspect the quality of the insulating layer by several methods. Currently, the preferred inspecting method includes Tenco particle inspection using the American Tenco AIT-type machine. Generally speaking, the insulating layer can be considered a translucid layer. When an incident light radiates on the surface of the insulating layer, it usually generates both refraction and reflection. The reflective light reflects back from the surface of the insulating layer and the refractive light penetrates the insulating layer. Therefore, engineers usually term the insulating layer the translucid layer.
A conventional method to inspect a defect on a translucid film is Tenco particle inspection. First, an incident light is provided, for example, laser light with a predetermined angle. The incident light radiates on the surface of the translucid layer to inspect a defect particle on the translucid layer. The predetermined angle is determined to make total reflection on the translucid layer. The reflective light reflects from the translucid layer and is collected by Tenco inspectors. The reflective lights reflecting from different regions of the translucid layer, for example, different dies, have different light messages.
FIG. 1 showing a conventional method of inspecting a defect on a translucid film. First, a semiconductor substrate 10 is provided. A translucid layer 11, for example, an oxide layer, is formed on the semiconductor substrate 10 by deposition. Polishing the translucid layer 11 is performed to flatten the surface of the translucid layer 11 using chemical mechanical polishing (CMP). After polishing, defect particles 12 are formed and dishes 14 are formed because of dishing effects. Then an inspecting step is performed. A laser light with a predetermined angle radiates on the translucid layer 11. There are reflections from different regions of the translucid layer 11. As shown in FIG. 1, light 13A totally reflects from the translucid layer 11 and light 13B which radiates on sidewall of the dish 14 partially reflects and partially refracts. Partial light 13B refracts through the translucid layer 11 and partial light 13B reflects from the surface of the translucid layer 11. Light 13C scatters because of the defect particle 12.
At the beginning, the incident light with the predetermined angle satisfies total reflection conditions. The predetermined angle is determined satisfying the total reflection angle. When the incident light radiates on the dish 14 which is formed because of dishing effect, the predetermined angle on the dish 14 is no longer the total reflection angle. Therefore, the incident light radiating on the dish 14 partially reflects and partially refracts. If the incident light partially refracts through the translucid layer 11, the partially refracting light then reflects on the semiconductor substrate 10. The reflecting light from the semiconductor substrate 10 disturbs the original incident light to generate variable light intensity. The variable light intensity (color variation) affects inspection, reducing the accuracy of inspection results.